Re: [PATCH 09/11] job control: reorganize wait_task_stopped()

[Tejun Heo]

Hello,

On Thu, May 12, 2011 at 05:42:47PM +0200, Oleg Nesterov wrote:
> On 05/11, Tejun Heo wrote:
> >
> > > Can't we push this patch ahead of these changes? I can merge it into
> > > ptrace branch.
> >
> > It doesn't really fix the problem tho.  The whole thing is full of
> > holes
> 
> Hmm. Could you explain?  (unless you mean ptrace holes)

I meant other cases, RUNNING -> STOPPED and EXIT_* transitions.
Sleeping wait(2) is reliable without grabbing siglock thanks to
setting TASK_INTERRUPTIBLE on start and events waking up the waiter
after updating the state, so wait(2) is guaranteed to check the states
at least once after change actually has happened.

WNOHANG disables that mechanism.  We probably can add another set of
memory barrier hackery to fix that, but that's gonna be ugly.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/